As an example of a vibration isolation device, one with a structure is known for example in which an insertion hole is arranged in a bracket member attached to the vehicle body side, an inner cylinder member insertingly arranged in the insertion hole is attached to the vibration source (an engine, motor, transmission and the like for example) side, and the inner periphery side of the insertion hole and the outer periphery side of the inner cylinder member are connected to each other by vibration isolation leg parts formed of a rubber-like elastic body.
In recent years, with the aims of reducing the weight and lowering the cost, it has been tried to form a bracket member of a resin material. For example, in Patent Literature 1, a technology is disclosed in which a bracket member is formed of a resin material, a metal plate is disposed on the inner peripheral surface of a mount attaching hole (insertion hole) arranged in the bracket member, and a main body rubber elastic body (vibration isolation leg part) is adhered to the metal plate, and thereby the main body rubber elastic body is fixed to the inner peripheral surface of the mount attaching hole.
According to the technology, because the metal plate is interposed between the main body rubber elastic body and the bracket member, even when a local concentrated load is applied by the main body rubber elastic body in inputting a large displacement, the concentrated load can be borne by the metal plate. Thus, the strength required for the bracket member can be made comparatively low, and enlargement for securing the strength of the bracket member can be suppressed correspondingly.
In the meantime, according to the conventional vibration isolation device described above, in addition to the technology that the metal plate is fixed to the bracket member by adhesion, a technology of fixing by mechanical engagement structure is also disclosed. According to the mechanical engagement structure, the production cost can be reduced by a degree an adhesive and its coating step can be made unnecessary.